Pennsylvania Game News - October 2020 - 62

attractive to many birds of conservation
interest, including Acadian flycatchers,
Louisiana waterthrushes, yellow-throated
vireos, red-shouldered and broad-winged
hawks, and blackburnian, worm-eating,
Kentucky and cerulean warblers.
Our bird sightings - gray catbird, blue
jay, eastern towhee, field sparrow and
ruby-crowned kinglet - were meager due
to the weather and because most of the
previously mentioned forest birds already
were on their way south for the winter.
Once we reached the wetland complex
with beaver ponds on either side of the
road, the trees and shrubs changed to
grassy meadow, shrubland and wetland
forest. The floodplain holds an especially
interesting forested wetland with great
plant diversity, including poison sumac,
white turtlehead, yellow marsh marigold,
five sedge and two grass species, and
royal, interrupted and marsh ferns.
We saw the shrub buttonbush and the
vine virgin's bower - both wetland species
- as well as thickets of alder, sometimes
eaten by beavers. They prefer aspen, followed, to a lesser degree, by willow. They
will, however, eat other tree barks.
In spring and summer, they switch to
non-woody vegetation, especially grasses
and aquatic plants.
For instance, a Mississippi study found
in the stomachs of beavers, material from
42 tree species, 36 genera of green plants,
four kinds of woody vines and a lump of
grasses, according to Ben Goldfarb in
his engaging book Eager, the Surprising, Secret Life of Beavers and Why They
Matter.
"Beavers," he wrote, "are among our
closest ecological and technological
kin," because they are "wildly creative
tool users who settle near water, share a
62

fondness for elaborate infrastructure, and
favor fertile valley bottoms carved by lowgradient rivers."
Before Europeans arrived in North
America, researchers calculate the continent had between 15 million and 250
million beaver ponds.
"The Lehigh River," Goldfarb wrote,
was "almost choked with beaver dams,
which helped form the 'Great Swamp' at
its headwaters..."
Beavers still change the landscape
and, by doing that, create prime songbird
habitat.
In a 2000 coastal Maryland study,
researchers found a single beaver pond
slashed the discharge of total nitrogen by
18 percent, phosphorus by 21 percent,
and total suspended solids - waterborne
particles classified as pollutants by the
Clean Water Act - by 27 percent.
These clever engineers build their
dams for food storage, shelter from
weather, and safety from predators - black
bears and coyotes in our area. Propelled in
water by their webbed feet, they can hold
their breath for 15 minutes. They also have
transparent eyelids that accommodate
underwater sight, and a second set of furlined lips that enable them to chew and
drag wood underwater without drowning.
Beaver fur consists of 2-inch coarse
guard hairs over a soft, thick, buoyant
and waterproof underfur. A Scrabble
tile-sized patch has as many as 126,000
individual hairs; much more than we
have on our heads. Their flat, scaly tails
are rudders and alarm systems and have
a net of tightly meshed blood vessels that
can regulate their temperature.
Beavers fell trees by balancing on their
back legs with their tails beneath their
bodies, and use their large teeth to chip
away at the trunk until the tree falls. Then
they gnaw off the branches and cut the
Pennsylvania Game News - October 2020

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